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Satellite Infrared Radiance Validation using the NAST-Interferometer, Larar et al., ITSC-15, Maratea, Italy, 5 October, 2006.

LaRCSD

ProteusBAE 146-300

Aqua

Satellite Infrared Radiance Validation using the NAST-Interferometer

A. Larara, W. Smithb,c, D. Zhoua, X. Liua

aNASA Langley Research Center, Hampton, VA bHampton University, Hampton, VA

CUniversity of Wisconsin, Madison, WI

International TOVS Study Conference (ITSCInternational TOVS Study Conference (ITSC--XV)XV)October 5, 2006, October 5, 2006, MarateaMaratea, Italy, Italy


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Topics• Motivation• Instrument systems & datasets • Validation methodology• Select spectral radiance comparison results • Summary & conclusions


LaRCSD • Post-launch validation activities are critical to verify

quality of satellite measurement system – Sensor, algorithms, and direct/derived data products

• Resulting data contribute toward essential cal/val activities– On-orbit sensor performance verification & calibration validation– Algorithm validation– Direct and derived data product validation– Long-term monitoring of system performance (radiance &

geophysical)

• Aircraft underflights fundamental to validation task– High-altitude a/c instrumented with validation sensors (e.g., NAST-I,

S-HIS, & ARIES) provide critical validation data spatially & temporally coincident with satellite platforms of interest (e.g. Aqua (AIRS), and future Metop (IASI), NPP/NPOESS (CrIS), and GIFTS).

Motivation for satellite sensor cal/valand benefit from using airborne sensors


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The NAST & SHIS Systems

ER-2

InstrumentsIR Interferometer (NAST-I)

Spectral Range: 3.5 - 16 microns Spectral Res.: 0.25 cm-1 (ν/νδ > 2000 )Spatial res.: 130m/km flight alt.A/C platforms: ER-2, Proteus, WB-57 (soon)

Microwave Radiometer (NAST-M)Spectral Regions: 50 - 60 GHz, 113 - 119 GHz, 183 GHz, 425GHzA/C platforms: ER-2, Proteus, WB-57 (soon)

IR Interferometer (S-HIS)Spectral Range: 3 - 17 microns Spectral Res.: 0.5 cm-1 (ν/νδ > 1000 )Spatial res.: 100m/km flight alt.A/C platforms: ER-2, Proteus, DC-8, WB-57

Validation tools

NPOESS risk mitigation

Airborne science

Engineering testbeds


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Characteristics of Aqua Sensors Utilized

AQUA~ 1 km~13 – 128 cm-1, broadband filters

3.6 – 14.4 μ (IR bands 20 – 36) , discrete channels

Grating spectrometer

MODIS

AQUA~ 13.5 km~0.4 – 2.2 cm-1, υ/δυ ∼ 1200

3.8 – 15.4 μ, discrete channels

Grating spectrometer

AIRS

PlatformNadir IFOV

Spectral resolution

Spectral extentSensor typeInstrument system

Three consecutive MODIS scans, each consisting of ten 1-km lines. Partially overlapping scans at off nadir angles causes “bow tie” effect.


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NAST Participation in EAQUATE (European AQUA Thermodynamic Experiment):

International collaboration to validate radiance and geophysicalproducts obtained by the Atmospheric Infrared Sounder (AIRS)

aboard the Aqua satellite

Italian Campaign (Naples, Italy, 3 – 11 Sept. 2004):

NAST-I: 3.5-16 μm, 0.25 cm-1

NAST-M: 50-425 GHz (29 channels)S-HIS: 3.0-17 μm, 0.50 cm-1

FIRSC: 225-1000 μm, 0.1cm-1

µMAPS: 4.5-4.9 μm, (3 channels)

Potenza

United Kingdom (CranfieldUK, 11-19 Sept. 2004):

• US Proteus Aircraft

Cranfield

Ground sites:Potenza/Naples (lidar, radiosondes, aeri, m-wave)

UK BAE146-300 (ARIES, TAFTS, SWS, MARSS & Deimos; dropsondes; in-situ cloud phys. & trace species)

UK Met Office BAe 146-300

[ Note: => data used in present analysis]


LaRCSD • Incorporate multiple, independent, temporally- & spatially-coincident

datasets from the recent EAQUATE field campaign– Satellite:

• AQUA (AIRS & MODIS)– Aircraft:

• Proteus (NAST-I & S-HIS)• BaE-146 (dropsondes)

– Ground:• Potenza (lidar & radiosondes)

– “Model”:• ECMWF (T, q, O3)

• Verify spatial co-registration by comparing geo-referenced images at select λ

• LBL-based calculations for simulated radiance observations– Using various combinations for atm state “truth” data (i.e. ECMWF,

radiosondes, 2 independent Raman LIDAR systems, & dropsondes

• For clear, uniform regions over ocean and coincidence with ground site, compare high resolution spectra (i.e. NAST-I, S-HIS, AIRS, & “simulations”)

Radiance Inter-comparison Approach


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September 6, 2004 September 7,8 2004 September 8, 2004

September 9,10 2004 September 14, 2004 September 18, 2004

Italy Italy Italy

Italy UK UK

EAQUATE Proteus Mission Flight Tracks

Evening; Potenzaracetrack

Evening; Potenzaracetrack

Night; Aqua nadir

Night; Aqua nadir Day; Aqua nadir;

w/ BAe-146 Day; w/ BAe-146; both a/c at same z for segment


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EAQUATE 090704

MB31 stddev(AIRS IFOVs)max = 0.22 K

min = 0.05 K

mean = 0.11 K

stdev = 0.05 K

14.3 - 4 μ

NAST-I S-HIS AIRS

Spectra Comparison: NAST-I, S-HIS, AIRS


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Ocean Site 07Sept04NAST-I S-HIS AIRS SimulationECMWF sim

4.2 – 4.0 μ

8.1 – 7.4 μ

14.3 – 12.5 μ

11.5 – 9.9 μ

6.5 – 6.1 μ

ECMWF vs AIRS

AIRS vsNAST-I

S-HIS vsNAST-I

Simulation vs measured:

Measured vs measured:


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EAQUATE 090904

Measured vs measured:

AIRS vsNAST-I

S-HIS vsNAST-I

AQUA track

Proteus track

14.3 – 12.5 μ

6.5 – 6.1 μ

Radiosonde sim LIDAR sim

NAST-I S-HIS AIRS Simulation

Simulation vs measured: Measured vs measured:

Potenzaground site

RAOB vs AIRS

LIDAR vs AIRS

AIRS vsNAST-I

Uniform ocean scene

CO2 band

H2O band

MB31

MB31


min = 0.10 K

mean = 0.14 K

stdev = 0.02 K

ECMWF vs AIRS

Simulation vs measured:


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EAQUATE 091404


min = 0.07 K

mean = 0.16 K

stdev = 0.05 K

MB31Spectra Comparison: NAST-I, S-HIS, AIRS

Region for Spectra Comparison:

NAST-I, S-HIS, AIRS


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Ocean Site 14Sept04NAST-I S-HIS AIRS Simulation

ECMWF sim

14.3 – 12.5 μ

dropsonde sim

6.5 – 6.1 μ

Simulation vs measured: Measured vs measured:

AIRS vsNAST-I

S-HIS vsNAST-I

ECMWF vs AIRS

drops vsAIRS


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Importance of space / time coincidence

50 100 150distance from site (km)

0.0

0.5

1.0

1.5

2.0

time

from

gnd

mea

s (h

rs)

#NAST-I IFOVs avg = 1

lbl_prof_site_Paolo_2004S

50 100 150distance from site (km)

0.0

0.5

1.0

1.5

2.0

time

from

gnd

mea

s (h

rs)

#NAST-I IFOVs avg = 1

lbl_prof_site_RAOB_2004

RSS (meas-sim radiance residuals) shown for portion of 090904 NAST flight track

LIDAR RAOB

Best match (min RSS) closest in space/time to LIDAR location/time

Best match not coincident with RAOB launch location/time


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RAOB motion and thermodynamic state variability (090904)

RAOB ascent profile

distance from launch site

altitude

Flight track: position & time

NAST-I nadir IFOV track

RAOB track

Modisvariability within AIRS IFOVs

• Significant geophysical field variance exists along RAOB flight profile

• RAOB not representative of launch site atmosphere for non-uniform fields


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Summary & ConclusionsSummary & Conclusions• Post-launch validation activities are critical to verify quality of satellite

measurement system (i.e., sensor, algorithms, and direct/derived data products)

• Very favorable spectral radiance inter-comparison results obtained between AIRS and NAST-I, S-HIS, and simulations based upon ground-based lidar, ECMWF reanalysis fields, and radiosondes

• Spatial and temporal coincidence between observing systems crucial to differentiate between measurement uncertainty and geophysical field variability

• Airborne high resolution FTS systems enable (very-well-calibrated) emulation of other high-resolution and broadband IR instrument systems, offering a unique advantage for and critical component to s/c sensor cal/val• coincident a/c FTS observations provide best match to s/c AIRS measurements• airborne assets can enable cal/val anywhere, unlike fixed-location ground sites

• EAQUATE data are proving to be very useful for current AIRS direct/derived data product validation, and should serve to further refine methodologies for future advanced sounder (e.g. IASI & CrIS) post-launch validation activities

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